We propose a new method for detecting tropical cyclone genesis at an early stage by supposing merger of mesoscale midlevel vortices to be a common precursor event. The merger event serves as a selection mechanism and is a possible explanation of why only a small fraction of cloud clusters which meet the necessary conditions actually develop into tropical cyclones. The detection procedure uses satellite IR images which are available in near real-time. After tests using data for the Bay of Bengal basin for the years 1999--2001, a real-time test was conducted for the post-monsoon 2002 and pre-monsoon 2003 seasons. We found that the method was successful in detecting the formation of tropical cyclones 04B (2002) and 01B (2003) about 48 hours before they reached storm strength, and no storm escaped detection.